He stood on the roads around Eleusis and challenged passers-by to a wrestling match. The loser (always the passer-by) was murdered, though Cercyon promised his kingdom to anyone who won. He was eventually beaten and killed by Theseus, who took over the kingdom of Eleusis. Theseus won owing to his skill, rather than superiority in brute physical strength. With this, Theseus started the sport of wrestling. Pausanias, writing in the Roman era, tells this story in his "Description of Greece" (1.39.3); Bacchylides alludes to the event in his 18th Ode, written in the fifth century BC.

Cercyon's daughter, Alope, had an affair with (or was raped by) Poseidon, and she beget Hippothoon (or Hippothous). Cercyon had his daughter buried alive, but Poseidon turned her into the spring, Alope, near Eleusis.